System for controlling plural magnetic bearing devices from a remote location

ABSTRACT

A magnetic bearing device comprises a machine main body having position sensors for detecting the position of a rotary body and magnetic bearings for magnetically contactlessly supporting the rotary body, a controller for controlling the magnetic bearings based on the signals from the position sensors, a data processing computer installed at a location away from the controller, and modems for connecting the controller to the computer by communication lines.

This is a continuation of U.S. Application Ser. No. 08/841,810, filedMay 5, 1997.

BACKGROUND OF THE INVENTION

The present invention relates to magnetic bearing devices for rotating arotary body as magnetically supported by magnetic bearings withoutcontact.

Magnetic bearing devices, for example, for use in turbo molecular pumpsof the magnetic bearing type comprise a machine main body havingposition sensors for detecting the position of a rotary body andmagnetic bearings for magnetically contactlessly supporting the rotarybody, and control means for controlling the magnetic bearings based onthe signals from the position sensors. While many magnet bearing devicesproduced by a certain manufacturer are used by users at widely separatedlocations, the bearing devices are independent of one another and areconventionally controlled and maintained individually. Accordingly, themagnetic bearing device can not be checked for operating state or forthe diagnosis of failure at a place other than the actual location ofthe device (the site of installation of the device for the user).Although the device as installed requires periodic maintenance, themanufacturer is unable to recognize or grasp the operating state of thedevice as stated above, so that every time need arises, the manufacturermust dispatch the technician to the site for him to grasp the operatingstate or to diagnose failure and to thereafter adjust the control means.Since such work at the installation site must be performed for each ofthe magnetic bearing devices of the users at various remote locations,there is the problem that the work requires much time and labor. Furtherthe control circuits of the control means of magnetic bearing devicescomprise an analog circuit and digital circuit. In the case of eithercircuit, a need is likely to arise to improve or alter the magneticbearing control characteristics during use. In such an instance, themanufacturer must dispatch the technician to the site for the adjustmentof the control circuit as in the above case.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the foregoing problemsand to provide a magnetic bearing device which is accessible from aremote location for the recognition of the operating state thereof andfor the adjustment of control means thereof.

The present invention provides a magnetic bearing device characterizedin that the device comprises a machine main body having position sensorsfor detecting the position of a rotary body and magnetic bearings formagnetically contactlessly supporting the rotary body, control means forcontrolling the magnetic bearings based on signals from the positionsensors, data processing means installed at a location away from thecontrol means, and communication means for connecting the control meansto the data processing means by communication lines.

The communication means connecting the control means to the dataprocessing means allows data communication between the control means andthe data processing means, making it possible to grasp the operatingstate of the machine main body or to adjust the control means using thedata processing means as installed at a remote location.

The communication means, which is preferably one allowing interactivecommunication between the control means and the data processing means,is one at least enabling the control means to transmit communications tothe data processing means.

In the case where communications are transmitted only from the controlmeans to the data processing means, for example, data relating to theoperating state of the machine main body (e.g., data as to the positionof the rotary body or data as to control current values for the magneticbearings) is sent to the data processing means via the communicationmeans.

This enables the data processing means to recognize the operating stateof the machine main body. When the data processing means is installed atthe location of the manufacturer, therefore, the manufacturer can graspthe operating state of the machine main body without dispatching thetechnician to the installation site. It is also possible to diagnosefailure from the data relating to the operating state, and even if theresult of diagnosis indicates a need to adjust the control means at thesite, it is only the adjustment of the control means that must be madeat the site. The work time at the site can then be shortened. Further ifonly the adjustment of the control means is necessary, the user'stechnician may be able to meet the need.

In the case where the control means and the data processing means areadapted for interactive communication therebetween, the control means,for example, transmits data relating to the operating state of themachine main body to the data processing means through the communicationmeans, and the processing means transmits control parameters for themagnetic bearings to the control means through the communication means.

As in the foregoing case, the data relating to the operating state ofthe machine main body and transmitted from the control means to the dataprocessing means enables the processing means to grasp the operatingstate of the machine main body, while the control means can be adjustedby transmitting the magnetic bearing control parameters from theprocessing means to the control means. When the data processing means isinstalled at the location of the manufacturer, therefore, themanufacturer is able to recognize the operating state of the machinemain body, diagnose failure and adjust the control means withoutdispatching the technician to the site of installation. In this case,the data processing means may be adapted to automatically determine thedata as to the control of the magnetic bearings, such as magneticbearing control parameters, based on the machine main body operatingstate or the result of diagnosis of failure, or the technician maydetermine the data and input the data to the data processing means.

For example, the machine main body and the control means are provided inmore than one set.

The sets of machine main body and control means may be installed at onelocation or at a plurality of separated locations.

It is then possible to grasp the operating state of machine main bodiesat a remote location or remote locations or to grasp the operating statethereof and to adjust the control means by (one or a plurality of)common data processing means. Accordingly, the data processing means,when installed at the location of the manufacturer, enables themanufacturer to provide centralized supervision over the machine mainbodies and control means which are installed at various locations fordifferent users.

For example, the control means comprises an A/D converter for convertinganalog signals from the position sensors into digital position signalsand outputting the digital position signals, a digital signal processorfor determining control current values to be given to the magneticbearings based on the digital position signals and outputting the valuesas digital control signals, and a D/A converter for converting thedigital control signals into analog signals and feeding the resultinganalog signals to the magnetic bearings.

The term the “digital signal processor” as used herein refers tospecific hardware adapted to receive digital signals and to deliverdigital signals, programmable by software and operable for high-speedreal-time processing. The processor will hereinafter be referred to as“DSP.”

When provided with the DSP, the control means is capable of processingsignals at a high speed in real time.

For example, the control means comprises first memory means for storingdata relating to the position of the rotary body and obtained from theposition sensors and data as to the control current values determined bythe digital signal processor for the magnetic bearings, and secondmemory means for storing magnetic bearing control parameters transmittedfrom the data processing means through the communication means. Thedigital signal processor feeds the data relating to the position of therotary body and the data as to the control current values for themagnetic bearings to the first memory means, causes the first memorymeans to store the data and reads the magnetic bearing controlparameters from the second memory means for use as new controlparameters. The data processing means reads the data relating to theposition of the rotary body and the data as to the control currentvalues for the magnetic bearings from the first memory means through thecommunication means, transmits the magnetic bearing control parametersto the second memory means through the communication means and causesthe second memory means to store the parameters.

The data processing means is then able to grasp the operating state ofthe machine main body and to adjust the control means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the construction of a magnetic bearingdevice as a first embodiment of the invention;

FIG. 2 is a diagram showing the construction of a magnetic bearingdevice as a second embodiment of the invention; and

FIG. 3 is a diagram showing the construction of a set of machine mainbody and controller of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings.

FIG. 1 shows a first embodiment.

With reference to FIG. 1, the magnetic bearing device comprises amachine main body 1, controller 2 serving as control means, computer(e.g., personal computer) 3 serving as data processing means and twomodems 4, 5 serving as communication means. The machine main body 1,controller 2 and first modem 4 are installed, for example, at thelocation of a user, and the computer 3 and second modem 5 at a remotelocation, for example, at the location of the manufacturer. The twomodems 4, 5 are connected to communication lines 6, 7 such as telephonelines.

When the device is used as a turbo molecular pump of the magneticbearing type, the machine main body 1 serves as the pump main body. Themain body 1 has a shaftlike rotary body 8 vertically disposed within acasing (not shown). Also provided within the casing are an axialmagnetic bearing 9 and upper and lower two radial magnetic bearings 10,11 for magnetically contactlessly supporting the rotary body 8, an axialposition sensor 12 for detecting the position of the rotary body 8 withrespect to the axial direction thereof, upper and lower two radialposition sensors 13, 14 for detecting the position of the rotary body 8with respect to radial directions thereof, a built-in high-frequencymotor 15 serving as means for rotatingly driving the rotary body 8 at ahigh speed, and a rotational speed sensor 16 for detecting the speed ofrotation of the rotary body 8. Usually, the axial magnetic bearing 9comprises a pair of electromagnets 9 a, and each of the radial magneticbearings 10, 11 comprises two pairs of electromagnets 10 a or 11 a.These magnetic bearings 9, 10, 11, position sensors 12, 13, 14, motor 15and rotational speed sensor 16 are known and therefore will not bedescribed in detail.

The controller 2 serves to control the bearings 9, 10, 11 and the motor15. The controller 2 comprises a DSP 17, first EPROM 18 serving as firstmemory means, second EPROM 19 serving as second memory means, A/Dconverter 20, D/A converter 21, position sensor drive circuit 22, poweramplifier 23, rotational speed sensor drive circuit 24 and motor drivecircuit 25. The DSP 17 performs the control operation and communication,has a parallel link and modem ports allowing communication with anexternal device and is connected via the EPROMs 18, 19 to the firstmodem 4. The first EPROM 18 serves to store the data to be transmitted.The second EPROM 19 serves to store the program to be executed by theDSP 17 and the data received. The DSP 17 is connected to thecommunication lines 6, 7 by way of the EPROMs 18, 19 and the first modem4. The computer 3 is connected via the second modem 5 to thecommunication lines 6, 7. The modems 4, 5 have a communication capacityof at least 28800 bps.

The position sensors 12, 13, 14 are driven by the sensor drive circuit22. Based on the outputs from the sensors 12, 13, 14, the drive circuit22 detects the axial position of the rotary body 8 and the radialposition thereof at upper and lower two locations. The analog positionsignals from the sensor drive circuit 22 are converted by the A/Dconverter 20 into digital position signals, which are fed to the DSP 17.Based on the digital position signals, the DSP 17 controls the excitingcurrents of the electromagnets 9 a, 10 a, 10 b of the respectivemagnetic bearings 9, 10, 11. Digital control signals corresponding tocurrent command values from the DSP 17 are converted by the D/Aconverter 21 into analog control signals, based on which the poweramplifier 23 supplies exciting currents to the respective electromagnets9 a, 10 a, 11 a, with the result that the rotary body 8 is contactlesslysupported at a specified position with respect to the axial and radialdirections. The rotational speed sensor 16 is driven by the sensor drivecircuit 24, which detects the speed of rotation of the rotary body 8from the output from the sensor 16. The sensor drive circuit 24 feeds arotational speed detection signal to the DSP 17, which in turn controlsthe speed of the rotary body 8 based on the detection signal. The DSP 17delivers a rotational speed command signal to the motor drive circuit25, which in turn drives the motor 15 based on the signal. Consequently,the rotary body 8 is rotated at a predetermined speed. The detection ofthe position of the rotary body 8, detection of the rotational speed ofthereof, production of the current command value and delivery of therotational speed command value are made at a predetermined timeinterval.

Every time the position and rotational speed of the rotary body 8 aredetected during the operation of the magnetic bearing device, the DSP 17stores the position data and speed data in the first EPROM 18. Everytime the current command value is delivered, the DSP stores the commandvalue data in the first EPROM 18. These items of data are then sent fromthe first EPROM 18 to the computer 3 via the first modem 4,communication line 6 and second modem 5. Thus, the operating state ofthe machine main body 1 can always be monitored and grasped at a remotelocation. Further when required, the control characteristics of thecontroller 2, such as the control parameters for the magnetic bearings9, 10, 11, the predetermined speed of the motor 15 and sampling timeinterval, can be altered on the computer 3. The altered data istransmitted to the controller 2, whereby the control characteristics ofthe controller 2 can be adjusted from the remote location. The data thusset by the computer 3 is sent to the DSP 17 via the second modem 5,communication line 7, first modem and second EPROM 19 and is stored in aspecified location of the second EPROM 19. The machine main body 1 isthereafter controlled using the data thus stored, i.e., the alteredcontrol characteristics.

Although the controller comprises a DSP and two EPROMs in the case ofthe foregoing embodiment, the memory means within the DSP is usable forthe DSP only to constitute the controller. The memory means within theDSP is then usable as the first and second memory means.

Further according to the embodiment, the magnetic bearings 9, 10, 11 andthe motor 15 are under the control of the single DSP 17, whereas thebearings 9, 10, 11 only may be controlled by the DSP 17, with the motor15 made controllable independently by other control means.

FIGS. 2 and 3 show a second embodiment. Throughout FIGS. 1 to 3, likeparts are designated by like reference numerals.

The second embodiment comprises a plurality of sets of machine main body1 and controller 2. FIG. 2 shows the overall construction of themagnetic bearing device, and FIG. 3 shows one set of machine main body 1and controller 2 in greater detail.

In the case of the second embodiment, the controllers 2 of the sets areconnected via respective first modems 4 to a single server 30, which isconnected by ISDN 31 serving as communication lines to a second modem 5connected to a computer 3. The controller 2 and the first modem 4 ofeach set are assembled into a single control unit 32. The controller 2is equivalent to the controller 2 of the first embodiment from which thetwo EPROMs 18, 19 are removed, and the DSP 17 is connected to the firstmodem 4. The memory (not shown) incorporated in the DSP 17 serves thefunction of the EPROMs 18, 19. The construction of the rest of thecontroller 2 is the same as in the first embodiment. The machine mainbody 1 has the same construction as in the first embodiment.

With the second embodiment, communications are transmitted between thecomputer 3 and the controllers 2 of the sets in the same manner as inthe case of the first embodiment. In this case, data transmission fromthe controller 2 and data transmission from the computer 3 are effectedalternately.

When the control units 32 as installed for one user or for differentusers are connected to the ISDN 31 according to the second embodiment,the single computer 3 as installed at the location of the manufacturerthen provides centralized supervision over these control units. Thesingle computer 3 is connected to the ISDN 31 according to the secondembodiment, whereas if, for example, a plurality of computers 3 asinstalled at different locations are connected to the ISDN 31, the setsof machine main body 1 and control unit 32 can be supervised in acentralized manner at any of these locations.

What is claimed is:
 1. A system for controlling plural magnetic bearingdevices, the system comprising: a) a plurality of machine main bodies,each machine main body including: 1) position sensors for detecting theposition of a rotary body; 2) magnetic bearings for magneticallycontactlessly supporting the rotary body; and 3) a motor for rotatinglydriving the rotary body at a predetermined speed; b) at least onecontroller for controlling the magnetic bearings based on signals fromthe position sensors and for controlling the motor based on signals fromthe position sensors, each said at least one controller said at leastone controller including: 1) an analog-to-digital converter forconverting analog signals from the position sensors into digitalposition signals and for outputting the digital position signals; 2) adigital signal processor for receiving the digital position signals andfor determining control current values to be given to the magneticbearings based on the received digital position signals and foroutputting the control current values as digital control signals, thedigital signal processor including: i) means for feeding first data,second data and third data to a first memory means for storage; and ii)means for reading magnetic bearing control parameters from a secondmemory means, for use as new control parameters; 3) a digital-to-analogconverter for converting the digital control signals into analog signalsand for feeding the analog signals to the magnetic bearings; 4) thefirst memory means for storing: i. the first data relating to a positionof the rotary body, obtained from the position sensors; ii. the seconddata as to the control current values determined by the digital signalprocessor for the magnetic bearings; and iii. the third data relating tothe speed of the rotary body; 5) the second memory means for storing: i.a program to be executed by the digital signal processor; and ii. themagnetic bearing control parameters, transmitted from a data processingmeans through a communication means; 6) a motor drive circuit forreceiving the new control parameters relative to the predetermined speedof the rotary body and driving the motor based on the controlparameters; c) the data processing means installed at a remote locationaway from the system for controlling said plural magnetic bearingdevices, the data processing means including: 1) means for reading thefirst data and the second data from the first memory means through thecommunication means; and 2) means for transmitting the magnetic bearingcontrol parameters to the second memory means through the communicationmeans; and d) the communication means for connecting the system forcontrolling said plural magnetic bearing devices to the data processingmeans by modems corresponding to respective control means andcommunication lines.
 2. The system of claim 1, wherein: thecommunication lines include telephone lines.
 3. The system of claim 1,wherein: the communication lines include integrated services digitalnetwork (ISDN) lines.
 4. The system of claim 1, further comprising: aserver, connected to the communication lines, for connecting theplurality of control means to the data processing means.